Shivering is the most basic method of maintaining core body temperature during cold exposure, but the human body also has a typically dormant, currently untapped metabolic pathway, which preferentially burns fat for fuel, producing heat. This pathway is called non-shivering thermogenesis. The organ that operates this pathway is called brown adipose tissue (“BAT”).
To elaborate, when the human brain begins to sense that the body is exposed to cold temperatures, the brain releases signals to activate BAT. When BAT is activated, levels of uncoupling protein 1 (“UCP-1”) are increased, which turns on the entire BAT fat-burning system. When UCP-1 levels are increased in BAT, the body begins to burn body fat.
When adipose tissue or cells, also known as fat tissue, take up nutrients, the adipose tissue typically uses them to produce adenosine triphosphate, thus storing energy for later use. However, UCP-1 effectively disables this process, by targeting the stored energy and burning the stored energy as heat, resulting in an increase in metabolism, and ultimately warming the body during cold stress.
Research shows that BAT activity is higher in lean individuals than in overweight individuals, declines as an individual ages, and also decreases with prolonged dieting. Conversely, activation of BAT in animals and humans results in higher metabolic rates, increases in fat burning, and improves insulin sensitivities. There is a significant inverse correlation between obesity and brown fat levels in the body, with brown fat tending to be higher in lean people than in obese people. Furthermore, when people diet (maintain a caloric deficit) for a sustained period of time, there is a decline in BAT and UCP-1 activity. This suggests that brown fat levels in the body can play an important role in body fat regulation. Thus, BAT activity in the body, or the lack thereof, and/or distribution of BAT in the body, may explain why individuals reach diet plateaus or why some people struggle with weight loss more than others.
Since the discovery of BAT, scientists have been seeking ways to activate dormant BAT in humans, with little success. Previous research has demonstrated that capsaicinoids, and grains of paradise, particularly 6-paradol, are potent brown fat activators. These ingredients were clinically shown to increase metabolism through brown fat oxidation. See M. Iwami et al., Extract of grains of paradise and its active principle 6-paradol trigger thermogenesis of brown adipose tissue in rats, 161 AUTON NEUROSCI. 63 (2011); J. Sugita et al., Grains of paradise (Aframomum melgueta) extract activates brown adipose tissue and increases whole-body energy expenditure in men, 110 BR. J. NUTR. 733 (2013). However, this same research demonstrates that certain individuals do not respond to the grains of paradise treatment and were termed “non-responders.” The non-responders were identified to be “BAT negative” people who did not respond because they lacked the necessary amount of brown fat to be activated. Furthermore, there is a significant correlation between obesity and brown fat levels in the body, demonstrating that brown fat levels in the body can play an important role in body fat regulation.
Irisin is the first hormone identified that is specifically secreted from muscle tissue. Scientists are advertising irisin as the next exercise pill. Irisin was discovered in 2012 and named after the Greek messenger “Iris.” Research shows that exercise in humans and animals increases this hormone in muscle, and its increase can be detected in the plasma as well as in muscle and adipose tissue. Irisin travels to adipose tissue, where it increases fat burning and metabolism. In particular, irisin causes “browning” of fat, turning inactive white fat into metabolically active BAT. See, e.g., P. Boström, et al., A PGC1-α-dependent myokine that drives brown-fat-like development of white fat and thermogenesis, 481 NATURE 463 (2012); Jorge I. Castillo-Quan, From white to brown fat through the PGC-1-α-dependent myokine irisin: implications for diabetes and obesity, 5 DISEASE MODELS & MECHANISMS 293 (2012); F. Villarroya, Irisin, turning up the heat, 15 CELL METABOLISM 277 (2012); D. P. Kelly, Irisin, Light My Fire, 336 SCIENCE 42 (2012); M. Elsen et al., Browning of white fat: Does irisin play a role in humans?, 222 J. ENDOCRINOLOGY R25 (2014).
To date, no supplement or food has been shown to demonstrate activation of irisin; nor has a drug been developed for use in humans. Thus, such agents would have tremendous implications for weight loss.
Thus, there exists a current need for a unique composition including irisin-stimulating ingredients that could activate irisin to promote the “browning” of white adipose tissue so that it behaves like BAT, and/or BAT-activating ingredients, which could in turn increase metabolism and enhance weight loss.